1. Field of the Invention
The present invention relates to system for spotting moving objects based on a plurality of satellites in which the position of moving objects dispersedly existing in space near the earth can be determined in real time by using imaging devices respectively mounted on a plurality of artificial satellites in orbit near the earth.
2. Description of the Related Art
In general, observation of moving objects orbiting in space near the earth is customarily performed by using an optical telescope or radar which is located on the earth. In observation by optical telescopes, a light spot not of a fixed star is extracted from images observed by these and its relative position is deduced with respect to the fixed stars. It is tracked for a certain time span to determine the orbit of the moving object. In observation by a radar, the pointing direction of an antenna and the range to a moving object are measured for a certain time span by receiving a reflected wave of transmitted radio waves, thereby determining the orbit of the moving object.
In observation by optical telescopes, however, in addition to the fact that an observation period is limited to during nighttime, the accuracy in observing the position of light spots is restricted due to scattering and/or refraction through the air. Also, since there are limits on the performance of imaging devices, the dimensions and/or clearance of observable objects are also limited.
In observation by radar, on the other hand, though an observation period is not limited to during nighttime, there are restrictions on the dimensions and/or clearance of observable objects similarly to the observation by optical telescope, in addition to the limits of the accuracy in determining the orbit of the moving object depending on the precision in detecting the angle of the antenna's attitude. It is necessary to increase transmitting power and to additionally increase the size of the antenna in order to achieve a higher observational performance, making readily imaginable its inherent limits in observation.
Further, of the above described two methods, the observation by optical telescope requires a massive data of fixed star distribution in order to instantly discriminate a moving object from the fixed stars. If collation with such data is not possible, a moving object can be specified only by continuing an uninterrupted observation for a certain time period so as to observe a change in the relative position between the moving object and the fixed stars. It is therefore readily imaginable that considerable observation time and costs are required for example for the task of specifying the orbits of space debris (generically referring to floating objects in space) which quite likely will be increased at an accelerated rate.